1. Field of the Invention
The present invention relates to a control device for hybrid vehicles, and in particular, relates to a control device for hybrid vehicles, which can improve the fuel consumption efficiency by conducting cylinder deactivated driving under certain vehicle driving conditions.
2. Description of the Related Art
Conventionally, hybrid vehicles having an engine and a motor as a drive source are known. Among hybrid vehicles, one type of hybrid vehicle called a parallel hybrid vehicle is known, in which an output of the engine is assisted by a motor.
In the above-described parallel hybrid vehicle, a control apparatus drives the motor for assisting the engine when the vehicle is in the acceleration mode, and the battery is charged by deceleration regeneration of the motor when the vehicle is in the deceleration mode, such that the vehicle can respond to the driver's demands while ensuring the remaining battery charge (electric energy). Because the hybrid vehicle is formed by connecting the engine directly with the motor, this parallel hybrid vehicle has an advantage in that the structure is simple and the total system can be light in weight, thereby improving equipment installation capability in the vehicle.
In order to eliminate the effect of friction (engine braking) of the engine at the time of deceleration regeneration, several mechanisms have been proposed, such as a mechanism, which includes a clutch between the engine and the motor (for example, Japanese Patent Application, First Publication No. 2000-97068), and a mechanism, in which the engine, the motor, and the transmission are connected in series (for example, Japanese Patent Application, First Publication No. 2000-125405).
However, the mechanism comprising a clutch between the engine and the motor have drawbacks in that the structure becomes complicated by inserting the clutch and the installing capability of the vehicle is reduced so that insertion of the clutch reduces transmission efficiency of the power transmission system. In contrast, when the engine, motor, and the transmission are connected in series, a problem arises in that the above-described friction of the engine reduces the regeneration energy and the regeneration energy is reduced so that the assist amount by the motor is limited.
A measure to reduce the friction loss of the cylinder at the time of deceleration is proposed to control the throttle valve in the opening side in the deceleration mode of the vehicle by employing an electronic controlled throttle mechanism for sharply reducing the pumping loss and for increasing the regeneration which occurs during deceleration. However, the above measure has a problem in that, because fresh air is introduced into the exhaust system, the temperatures of a catalyst or an A/F (air/fuel) sensor arc reduced so that the optimum control of the exhaust gas is degraded.